The present invention relates to a loudspeaker apparatus for an electronic keyboard musical instrument such as an electronic piano or the like.
As a loudspeaker apparatus for such an electronic keyboard musical instrument, there is conventionally known such a one as shown in FIG. 4(A) and FIG. 4(B). In this apparatus, a pair of right and left sound emission openings b, b are provided in a shelf board "a" of a casing f of the musical instrument. Each of loudspeakers c, c which are responsive to lower acoustic frequencies (e.g., woofers) is mounted on the shelf board "a" in alignment with the respective fringe of the sound emission openings b, b. Each of loudspeakers d, d which are responsive to higher acoustic frequencies (e.g., tweeters) is mounted on the shelf board "a" in close proximity to the loudspeakers c, c. Further, as shown in FIG. 5(A) and FIG. 5(B), there is known another loudspeaker apparatus in which speaker boxes e, e, each containing therein a loudspeaker c which is responsive to lower acoustic frequencies and a loudspeaker d which is responsive to higher acoustic frequencies, are mounted on the right and the left sides of the shelf board "a."
The speaker apparatus shown in FIG. 4(A) and FIG. 4(B) has a disadvantage in that, because there is no speaker box, the low-frequency range characteristics are poor. In the speaker apparatus shown in FIG. 5(A) and FIG. 5(B), since the speakers c, d are provided inside the casing f of the musical instrument, the sounds emitted from the speakers c, d interfere with each other within the casing f of the musical instrument or resonate with the casing f of the musical instrument. As a consequence, unnecessary resonated sounds will occur, resulting in a disadvantage in that good reproduced sounds are hard to be obtained.